Devices have been developed for creating oscillatory motion in phase opposition in dry shaving apparatus. For example, DE 1 151 307 A describes an oscillating armature drive for dry shaving apparatus with reciprocating working motion. The oscillating armature drive includes a U-shaped electromagnet formed fast with the housing of the shaving apparatus. Arranged in the proximity of the poles of the stationary electromagnet are a working armature and on either side of the working armature in mass symmetry a respective oscillatory compensating armature. In operation, the working armature, which drives the shaving cutter, oscillates parallel to the pole faces of the electromagnet, and the compensating armatures perform an oscillatory motion in phase opposition.
Another example, DE 196 80 506 T1 discloses an electric shaving apparatus having a linear oscillating motor with a stationary electromagnet and several movable components that are set in oscillation in phase opposition to each other by means of the electromagnet. To maintain the mutual phase relationship of the movable components also under load, said components are interconnected by means of a linkage mechanism that transfers the oscillatory motion from the one movable component to the other with simultaneous reversal of direction.
Another example, DE 197 81 664 C2 discloses a linear drive having a hollow cylindrical stator with an electromagnetic coil. Arranged in the stator are two movable elements that are driven in phase opposition to each other, the one element driving a shaving cutter while the other element may have a counterweight to suppress unwelcome vibrations.